(1) Field of the Invention
The present invention relates to a pellet implanting gun apparatus for subcutaneously implanting medicament containing pellets into animals without damaging the pellets. More specifically, the invention relates to a pellet implanting gun apparatus which provides for dual actuating means actuated by a trigger. Following insertion of the needle into the animal, the first actuating means urges the pellet through a needle and into the in vivo site of choice. Thereafter, the second actuating means mechanically retracts the needle from the animal leaving behind the first actuating means momentarily. The pellet is thus implanted in the animal, unobstructed by the needle so that there is no chance of damaging the pellet while manually removing the needle from the animal. This permits tissue, which is elastic, to close down over the pellet and to hold the pellet in place.
In other implanters of the prior art, a lot of pressure is placed on pellets during implanting and the pellets have a tendency to become pulverized, cracked, or otherwise damaged during the implanting process. This is especially true during the time when the needle is being manually removed from the insertion site. The present invention overcomes this problem by mechanically retracting the needle from around the pellet immediately after the pellet is implanted in the animal while simultaneously permitting the first actuating means to remain in situ until the hollow needle is withdrawn. This greatly reduces pellet damage during implanting and represents a significant improvement over the prior art.
(2) Prior Art
The prior art has described various types of pellet implant devices. These devices are designed to either retract the pellet drive rod from the needle after the pellets have been urged into the needle or they are designed to only retract the needle from the animal after the drive rod has urged the pellets into the needle. Illustrative of the prior art pellet implant apparatuses are U.S. Pat. No. 4,105,030 to Kercso; U.S. Pat. No. 4,154,239 to Turley and U.S. Pat. No. 4,687,465 to Prindle et al.
Kercso describes an implant apparatus comprised of a track mounted on a handle providing a front and a back track support. A detachable needle is mounted on the front of a retractable carriage that moves along the track. A passageway through the needle corresponds with a passageway through the carriage. A drive rod detachably attaches to the back track support so that the drive rod extends through the carrier passageway and partially through the needle. At least one pellet is placed in the needle passageway adjacent to the drive rod. The needle is then thrust into an animal and a pivotable trigger on the handle is squeezed which releases a propulsion device which retracts the needle from the animal. The drive rod is then manually pulled from the animal, leaving the pellet behind. Before the drive rod is pulled from the animal, there is a great likelihood that the animal will move, often violently, which can cause the pellet to become damaged by the drive rod.
Turley describes a pellet implanter comprised of a trigger pivotably attached to a housing which supports a hollow needle at a forward end. A plunger pin mounted on a shuttle is provided on the housing with the plunger pin aligned to pass through the needle. Pellets are positioned in a chamber between the needle and the plunger pin while a flexible cord extends from one end of the shuttle to the top of the trigger. The needle is inserted into an animal and when the trigger is squeezed, the cord pulls the plunger pin through the pellet chamber and into the needle. The needle is then manually extracted from the animal, leaving the pellets behind. A return spring, secured between the back of the shuttle and the housing causes the plunger pin to be extracted from the needle when the handle is released. Manually extracting the needle from the animal is known to cause the pellets to sometimes crack or become pulverized.
Prindle describes a pellet implanter apparatus comprised of a handle assembly that provides for a drive rod that is linearly moveable in a pistol grip by a pivotable linkage between a trigger and a holder for the drive rod. The proximal end of the linkage has a slot which slides on a roller bearing on the trigger and a distal end which is in slideable relationship through the holder for the drive rod. The proximal end of the linkage rotates in an arc on the roller bearing in the slot while the linkage pivots on a pin on the trigger in an arcuate slot in the trigger against the tension of a spring. When the trigger is squeezed, the distal end of the linkage pushes the rod holder and the drive rod out of the handle assembly, through an opening in a pellet carrier and out of a barrel of a needle to implant a pellet. The implanter apparatus is particularly adapted to implant pellets in animals, particularly as medicament pellets.